I. Field of Invention
This invention relates to wireless communications systems. Specifically, the present invention relates systems and methods for allocating traffic channels and supplemental channels in a base station or base station transceiver subsystem (BTS).
II. Description of the Related Art
Cellular telecommunications systems are characterized by a plurality of mobile stations (e.g. cellular telephones, mobile units, wireless telephones, or mobile phones) in communication with one or more base station transceiver subsystems (BTSs). Signals transmitted by the mobile stations are received by a BTS and often relayed to a mobile switching center (MSC) having a base station controller (BSC). The MSC, in turn, routes the signal to a public switched telephone network (PSTN) or to another mobile station. Similarly, a signal may be transmitted from the public switched telephone network to a mobile station via a base station or BTS and an MSC.
Each BTS covers a xe2x80x98cellxe2x80x99 within which a mobile station may communicate. A cell covers a limited geographic area and routes calls from mobile stations to and from a telecommunications network via an MSC. The coverage area of a typical cellular telecommunications system is divided into several cells. Different communications resources such as frequencies are often allocated to each cell to maximize communications system resources. When a mobile station moves from a first cell to a second cell, a handoff is performed to assign new system resources associated with the second cell.
A handoff involves the execution of a set of negotiation instructions between the mobile station and one or more governing BTSs and/or MSCs. Cellular telecommunications systems generally require efficient and reliable handoff procedures to maximize the utilization of system resources. Efficient and reliable handoff procedures are becoming increasingly important as smaller cells are deployed to meet demands for increased communications system capacity. Use of the smaller cells increases the number of cell boundary crossings and frequency assignments thereby increasing the need for efficient and cost-effective handoff mechanisms and procedures.
To facilitate handoff between adjacent cells, a handoff beacon is often employed. A beacon in each cell broadcasts a signal having a limited range about the cell. When a mobile station in a first cell detects a beacon from a second cell, the telephone is handed off to the second cell.
A BTS routes calls between mobile stations within a predetermined geographic area, i.e., cell governed by the BTS, and to and from an MSC and a BSC. The MSC and BSC facilitate the routing of calls between BTSs and between the wireless communications network and the PSTN, i.e., wireline network.
A BSC or MSC is often associated with a particular geographic area comprising one or more cells and often includes various components such as a selector bank subsystem (SBS) and radio link manager (RLM) to facilitate the allocation of network resources between voice calls and other network functions. Network resources may include computer memory, bandwidth, and other hardware and software.
Typically some network resources are assigned to traffic channels and some network resources are assigned to supplemental channels. The use of traffic channels and supplementary channels in wireless telecommunications networks is discussed in IS-95 telecommunications industry standard documentation.
Supplemental channels often carry data such as a file transferred between two wireless computer modems. Fundamental traffic channels often carry voice calls and/or data calls over the wireless network. To improve the quality of a given voice and/or data call, additional supplemental channels may be added to the traffic channel associated with the voice and/or data. The additional supplemental channels increase the throughput of the wireless link between the mobile station and the base station.
When a mobile station, maintaining a call, travels from a first system coverage area associated with a first BSC (or BTS) to a second system coverage area associated with a second BSC (or BTS), the mobile station is handed off to the second BSC (or BTS) and associated BTS(s). If the target BTS associated with the second BSC (or BTS) has insufficient traffic channels to accommodate the handoff, the handoff is typically blocked by a call resource manager (CRM) of the target BTS, and the call is dropped. Hence, when all traffic channels in a BTS are in use, any additional calls handed off to the BTS are typically dropped, and any newly originated calls are typically blocked.
Hence, a need exists in the art for an efficient and cost effective system for reducing dropped or blocked calls due to insufficient traffic channel resources. There exists a further need for an efficient method for allocating and de-allocating traffic channels and supplementary channels.
The need in the art is addressed by the system for managing wireless communications system resources of the present invention. In the illustrative embodiment, the present invention is implemented in software running on a computer within a base station in a wireless communications system and includes a first mechanism for determining currently available wireless communications system traffic resources and providing a signal in response thereto. A second mechanism de-allocates wireless communications system supplemental resources and reallocates the supplemental resources as traffic resources in response to the signal.
In a specific embodiment, the currently available wireless communications system traffic resources include currently available traffic channels, and the supplemental resources include supplemental channels. The first mechanism includes code for comparing a number of in-use traffic channels with a number of total traffic channels and providing the signal when the difference between the number of total traffic channels and the number of in-use traffic channels is less than a predetermined threshold.
The first mechanism further includes code for monitoring when a call handoff request is blocked at a base station call resource manager and providing the signal when the call is blocked. The second mechanism includes code for sending a message to a selector bank subsystem radio link manager, receiving a response from the selector bank subsystem radio link manager, de-allocating the supplemental resources, and reallocating the supplemental resources as traffic resources.
In the illustrative embodiment, the invention is implemented in software running on a computer within the wireless communications network that strategically controls, via the first and second mechanisms, the allocation of supplemental channels in response to changing network traffic. By strategically controlling the allocation of supplemental channels, the present invention reduces dropped or blocked calls during handoffs, reduces blocked or dropped calls during call origination, and increases the overall reliability of the associated wireless communications system.